1. Field of the Invention
The present invention relates generally to the construction of knives and other sharpened implements. The invention particularly relates to the construction of knives to be used a surgical instruments, and more particularly to the construction of scalpels having an integral cover to protect such implements from damage and from damaging their surroundings.
2. Description of the Prior Art
Surgical scalpels are extremely sharp cutting implements. The extreme sharpness of the blades renders them very hazardous when passing the scalpels back and forth between the surgeon and the operating assistant. It is obvious that extremely sharp scalpels can very easily cut a glove, and the skin beneath the glove; and, if the blade has already been used on a patient, there is an obvious danger of infection. Another difficulty with such extremely sharp knives is that the blades are very easy to ruin, for example, by the scalpel edge coming in contact with another instrument, an instrument tray or other hard surface.
There have been a number of attempts to overcome these problems. U.S. Pat. No. 2,735,176 discloses a veterinary surgical knife which comprises a hollow handle component having a slidably extendable blade. U.S. Pat. No. 4,730,613 and U.S. Pat. No. 4,663,846 disclose cutting instruments having a extendable blades. U.S. Pat. No. 4,491,132 discloses a sheath and a retractable surgical tool combination wherein the blade must be manually extended and retracted in relation to the sheath. U.S. Pat. No. 4,523,379 discloses a knife with retractable sheath, teaching a complex retraction mechanism wherein the sheath must be manually extended to cover the blade, and wherein the blade is exposed when the sheath is in its relaxed position. None of the foregoing are designed to be disposable items U.S. Pat. No. 4,735,202 discloses a disposable microsurgical knife having a locking blade guard which must be manually extended to cover the blade, and, when retracted, is designed to be removed completely from the knife. U.S. Pat. No. 4,414,974 discloses a disposable microsurgical knife having a glow-in-the-dark shroud which must be manually extended to cover the blade and when extended is not locked in place. U.S. Pat. No. 3,906,626 discloses a disposable surgical scalpel in which the sheath must be manually extended to cover the blade, and, once fully extended, is permanently locked in its extended position.
The surgical scalpel of this invention obviates many of the prior art problems. First, its mechanism is simple, inexpensive, and easy to assemble, making it ideal for one-time use. Second, in its released position, the sheath is automatically extended to cover the blade so that manual sheathing of the blade is unnecessary. Third, the blade cannot be accidentally exposed by bumping the sheath. Fourth, the knife can conveniently be simultaneously held and unsheathed with one hand.